1. Field of the Invention
The present invention relates to a new lining material for pipe lines, especially for gas pipe lines or city water conduits. More particularly, the present invention relates to a new tubular lining material for lining pipe lines therewith which contain a plurality of portions different in inner diameter and/or a number of complicated bends and curved portions in a single pipe line system.
2. Description of the Prior Art
It is well known that superannuation or damage of pipe lines for gas or water often causes dangerous leakage of gas or water. When such pipe lines are buried in the ground, damage of the underground pipe lines caused by external force or superannuation will induce an extremely dangerous burst of gas or water. Especially, in case of rupture of the underground pipe lines caused by superannuation, it usually occurs suddenly and is not predictable. A sole effective countermeasure in the past to prevent such troubles is that before such underground pipe lines have well been superannuated, the pipe lines are dug up over the length in the order of several ten or hundred meters and replaced with new ones. As a matter of course, much labor power and time as well as costs are required for exchange of the pipe lines in addition to difficulty in the pipe-exchange work itself. Further, supply of city gas or water has to be discontinued for a long period of time until the pipe-exchange work has been finished. In case the pipe lines are buried under the public roads, people encounters a great deal of trouble and inconvenience since any traffic on the roads is limited for a long distance during the pipe-exchange works. However, such pipe-exchange work on the underground pipe lines over the almost full length thereof is utterly ineffective for the purpose of reinforcing the pipe lines against external force such as earthquake, heavy traffic loads or road-repairing works. In order to reinforce pipe lines against such external force, the individual pipe may be reinforced with a lining material prior to construction of the pipe lines. However, this countermeasure cannot be applied to pipe lines already constructed and buried in the ground.
Under the above particular circumstances, a primitive method for lining underground pipe lines wherein a flexible plastic tube is inserted into underground pipe lines and bonded to the inner surface thereof was proposed for attaining both purposes of repairing damaged portions of the pipe lines and reinforcing them so as to withstand mechanical shock by external force. In such method, however, the step for inserting the flexible tube into the underground pipe lines is extremely difficult so that the work is almost impossible to operate in such place where the pipe lines are long and/or curved. Several methods successively developed for improving this primitive method comprise inserting a flexible tube into pipes while turning the tube inside out by the action of a pressurized fluid, and bonding the tube onto the inner surface of the pipes by the aid of a binder. The methods of this type are disclosed in U.S. Pat. Nos. 2,794,758. 3,132,062 and 3,494,813 and British Pat. No. 1,069,623. These methods are in fact improved in the step of inserting a flexible lining tube into pipes but are still unsatisfactory in attaining the pipe-lining works for underground pipe lines. All of the methods disclosed in these patents require the previous application of a binder onto the inner surface of a pipe or tube prior to insertion of the tube. However, these prior art methods have a number of drawbacks; the quantity and distribution of the binder cannot be controlled so that the binder is applied unevenly onto the inner surface of the pipe, and moreover, when the pipe is inclined, the head pressure of the binder acts only on the top or turning point of the tube advancing within the pipe where evagination of the tube takes place so that the pressure required for evagination of the tube fluctuates and the amount of the binder applied tends to vary.
With a view to further improving these methods, new pipe-lining methods were proposed in U.S. Pat. Nos. 4,368,091 and 4,334,943 and have been watched in recent years as excellent methods for lining pipe lines, especially underground pipe lines with a flexible reinforcing tube. According to these methods, a tubular lining material is inserted into pipe lines while turning it inside out and applying at the same time a binder onto the inner surface of the lining material evenly and the lining material is bonded onto the inner surface of the pipe lines with the binder being interposed therebetween by the action of a pressurized fluid. The method disclosed in the last-mentioned patent involves, in addition to the above fundamental construction, an improvement wherein a rope-like elongated element is previously passed through a tubular lining material beyond the full length thereof prior to applying a binder evenly onto the inner surface of the lining material and, when the lining material is inserted into a pipe line from one end thereof and allowed to advance within the pipe line while effecting evagination of the lining material and simultaneous application of the binder onto the inner surface of the pipe line under fluid pressure, the rope-like elongated element is drawn at a constant rate from the opposite end of the pipe line, thereby reducing the high fluid pressure necessary for evagination and advancement of the lining material and controlling the evagination speed so as to prevent any locally uneven application of the lining material especially in curved portions of the pipe line. Up to date, the method disclosed in U.S. Pat. No. 4,334,943 is regarded as one of the most advantageous methods for lining gas pipe lines or city water conduits having a number of bends or curved portions and an inner diameter of about 100 mm or more.
On the other hand, various kinds of tubular materials have been used as lining materials for pipes or pipe lines. For example, a tubular lining material of a three-layer sandwich structure comprising the innermost tubular film substrate overlaid with a woven or unwoven fibrous material impregnated with a thermocurable resin (a thermocurable FRP lining material) and a removable outer layer is proposed in Japanese Patent Publn. No. 51-40595 (1976). However, such laminated tubular lining material cannot be used according to the previously mentioned advantageous lining method wherein evagination of the tubular material is utilized for lining pipe lines. Further, such laminated lining material cannot be applied onto the inner surface of pipe lines in bends or curved portions without formation of wrinkles. Several kinds of tubular lining materials comprised of an unwoven fabric layer and an impervious filmy layer are proposed in British Pat. Nos. 1,569,675, 1,340,068, 1,357,355 and 1,449,455; U.S. Pat. Nos. 4,009,063 and 4,064,211; and Japanese Patent Publns. Nos. 58-39646, 55-43890, 58-33098. A tubular laminate disclosed in British Pat. No. 1,569,675 is comprised of a felt of a synthetic fiber such as polyester fiber and a gas impermeable layer of a synthetic resin such as polyurethane. However, no attention is paid in this patent to how the tubular laminate can be applied in good compliance with the inner surface of pipe lines in curved portions, so that the lining material will naturally form wrinkles in the curved pipe lines. The remaining patents and patent publications disclose chiefly methods of lining pipe lines with a similar tubular laminate such as a needled felt or mat of a synthetic fiber coated with a synthetic resin. All of the lining methods disclosed in these patents and patent publications are inferior to the improved method disclosed in U.S. Pat. No. 4,334,943, particularly in that no attention is paid in these lining method to prevent occurrence of wrinkles and spaces in pipes in bends or curved portions. A tubular lining material comprised of a woven fabric and an impervious film of a synthetic resin is also disclosed in Japanese Laid-open Patent Appln. No. 56-8229. This tubular lining material is made of a textile jacket knitted or woven in a tubular form (with a warp of a polyester multifilament yarn and a weft of a twisted polyamide yarn) overlaid with a flexible natural or synthetic rubber and is distinguished by being laterally expandable on application of pressurized fluid for evagination. Accordingly, the use of a lining material of this type can show good compliance with local change in inner diameter of the pipe line and can reduce to a certain degree the tendency of forming wrinkles of the lining material and also a space between the inner surface of the pipe line and the lining material in a bend of the pipe line. However, this effect is still unsatisfactory when the pipe line has a number of bends or curved portions.
The tubular lining materials proposed hitherto are used exclusively for reinforcing gas pipe lines or city water conduits, which are relatively larger in inner diameter (about 200 mm or more in inner diameter). On the other hand, service pipe lines and house pipe lines branched from such relatively large pipe lines for the purpose of supplying gas or city water to individual consumers have an inner diameter of about 27 mm [25 mm (1 inch) in nominal inner diameter] in a straight pipe portion. The inner diameter of such service pipe lines or house pipe lines fluctuates locally or in curved portions within the range from about 22 mm to about 34 mm (about 12 mm in difference). In this case, the difference of about 12 mm in inner diameter reaches about 50% of a nominal inner diameter of the service or house pipe lines. In case of the larger pipe lines or conduits, on the contrary, the difference of about 12 mm in inner diameter is only several percents of an average inner diameter and is usually negligible. On account of such a very high rate of fluctuation in inner diameter, the lining treatment of service pipe lines and house pipe lines with a conventional tubular lining material was extremely difficult to work even according to the method disclosed in U.S. Pat. No. 4,334,943 regarded to be one of the most advantageous methods for lining pipe lines up to date.
With a view to protecting individual consumers' families, shops and offices from any dangerous burst of gas caused by unexpected damage of their service pipe lines or house pipe lines, it is also necessary to reinforce such pipe lines having a relatively small inner diameter with a lining material. Up to date, however, a tubular lining material which has elasticity in good compliance with a high rate of fluctuation in the inner diameter of such relatively small pipe lines and is thus considered to be suitable for reinforcing such pipe lines has not yet been proposed in references of this art. Under these circumstances, there is a great demand for developing a new tubular lining material which can be applied to pipe lines with an inner diameter of 25-200 mm, especially service pipe lines and house pipe lines, which have a number of bends or curved portions and a high rate of fluctuation in the inner diameter, without permitting occurrence of wrinkles in curved portions.